Set-MailboxDatabase –Identity ServerName\DatabaseName –IssueWarningQuota Size –ProhibitSendQuota Size –ProhibitSendReceiveQuota Size –DeletedItemRentention NumberOfDays

Set-MailboxDatabase –Identity Exchange1\SG01DB1 –IssueWarningQuota 200000 –ProhibitSendQuota 220000 –ProhibitSendReceiveQuota 250000 –DeletedItemRentention 30

Or…

Set-MailboxDatabase –Identity Exchange\SG01DB1 –IssueWarningQuota 200MB –ProhibitSendQuota 220MB –ProhibitSendReceiveQuota 250MB –DeletedItemRetention 30

I quite like that you can specify the limits in MB!

N3ilb